1. Field of the Invention
This invention relates to a cleaning device for cleaning a toner-image-bearing member such as photosensitive medium or the like to remove residual developer therefrom, and more particularly to improvements in such as cleaning device which uses a blade of resilient material.
2. Description of the Prior Art
The blade cleaning method utilizing a blade of resilient material is such that the edge of a blade formed of a wear-resisting resilient material such as rubber or the like frictionally slides relative to the surface of an image-bearing member such as photosensitive medium for electrophotography to thereby remove any residual substance including residual developer remaining on that surface.
This method, as compared with the conventional fur brush cleaning method, is higher in cleaning efficiency, and particularly so for the smooth-surfaced photosensitive medium in electrophotographic copying apparatus, for example, Se photosensitive medium or other photosensitive medium provided with an insulating layer of mylar or like material. Further, it eliminates the need for high-speed rotation which is required in the fur brush method, and it is also very simple in construction.
This leads to a very simple and compact construction of the device for carrying out such cleaning method, which in turn means very high effectiveness for large copying machines as well as small copying machines for office work.
In view of such effectiveness of the blade cleaning method, the applicant has studied, developed and proposed various types of arrangement for it. One of them is disclosed in detail in U.S. Pat. No. 3,859,691 by Katayama et al. and such an arrangement is shown in FIG. 1 of the accompanying drawings wherein the device is disposed sidewise of a photosensitive drum 1 to cause a blade 2 to scrape off developer D from the surface of the photosensitive drum rotating upwardly and the scraped-off developer drops from gravity into an underlying container 3 for collection therein. In such arrangement, the developer removed by the blade edge drops without building up on the edge portion, thus ensuring a good cleaning effect. This arrangement, however, restricts the position of the device to the area sidewise of the photosensitive drum. Especially, in view of the fact that the developing device is situated in underlying relationship with the photosensitive drum and an image transfer device or the like is adjacent thereto, it has structurally been quite restrictive in making the entire apparatus compact that the cleaning device occupies the position sidewise of the photosensitive drum.
An arrangement as shown in FIG. 2 of the accompanying drawings wherein the cleaning device is situated not sidewise of but above the photosensitive medium is structurally very effective. However, the simple overlying relationship of the blade with the photosensitive drum might permit developer to be stagnant on the blade portion, thus impeding the cleaning efficiency.
Even such as arrangement will still be effective if it is incorporated in the apparatus disclosed in U.S. Pat. No. 3,917,398 by Takahashi et al. As shown in FIG. 3 of the accompanying drawings which shows a side view of the arrangement, a cleaning blade 6 is urged against the surface of a photosensitive medium 5 provided over a drum 4. Disposed adjacent to the blade is a guide plate 7 which may be in slight pressure contact or in closely spaced apart relationship with the photosensitive medium. By the setting of this guide plate, toner particles such as removed developer and the like (hereinafter referred to as removed toner) are forced upwardly through the gap between the blade edge portion and the guide plate edge portion. The removed toner may of course be collected from the guide plate by appropriate means.
FIG. 4 of the accompanying drawings shows, in perspective view, an apparatus provided with such as cleaning device. A lead screw 8 for conveying removed toner is disposed over the clearance between the blade 6 and the guide plate 7 to convey the removed toner laterally. A delivery duct 9 is provided to guide and collect therethrough the removed toner conveyed by the screw 8 into the developer reservoir 11 of a developing device 10. Such a construction enables highly efficient cleaning.
However, it has been found that the attempt to reuse the removed toner by providing the cleaning device above the photosensitive drum encounters several problems.
Firstly, the toner removed by the blade edge portion is forced upwardly through the gap between the blade and the guide plate while spreading laterally along the blade edge, namely, axially of the drum. Thus, as viewed in FIG. 4, rather than at this end of the blade 6 connected to the duct 9 leading to the developing device 10, at the other end of the blade, the laterally moving toner will leak and scatter from said other end of the blade and/or the drum, resulting in contamination of the interior of the apparatus.
Secondly, scattering of the toner will also occur even at the delivery end of the blade which is adjacent to the duct 9. In the arrangement as shown in FIG. 4, the toner forced upwardly onto the cleaning blade 6 is advanced toward this side on the blade and on the guide plate 7 by the screw 8 and drops into the duct 9 at the point beyond this end of the photosensitive drum 5, and part of the toner will scatter upwardly when such drop occurs. Incidentally, for the mounting or dismounting of the photosensitive drum 5 or the cleaning device, the cleaning blade 6 and guide plate 7 must be separated from the drum 5 and usually the blade 6 and guide plate 7 are movably mounted by means of shafts 12 and 13, respectively. Thus, the cleaning blade 6 and duct 9 are movable relative to each other. Also, the guide plate 7 must keep uniform slight pressure contact with the photosensitive drum due to gravity or the like, and any strong contact thereof with other part which would impart non-uniform force to the guide plate is undesirable. For these reasons, it is difficult to provide complete sealing for the delivery portion between the cleaning blade 6 and the guide plate 7 and the duct 9, whereas any gap present in such portion would also permit the upwardly scattered toner in the delivery portion to leak therethrough and contaminate the interior of the apparatus.
In the gap between the blade edge and the guide plate, part of the toner is moved toward this side on the photosensitive drum 5 and drops into the duct 9 at this end of the photosensitive drum. Therefore, sealing is also requird between the duct 9 and this end of the photosensitive drum 5, but the requirement of rotatability of the photosensitive drum makes it difficult to provide complete sealing for such portion and thus, toner may also scatter therefrom to contaminate the interior of the apparatus.
Thirdly, the need to remove the photosensitive drum or the cleaning device from the apparatus arises from the purpose of maintenance and during such removal, a great deal of toner in the cleaning device may drop through the gap between the cleaning blade 6 and the guide plate 7 extremely contaminate the interior of the apparatus and even the neighboring floor or the like.
Further, when the cleaning device has been removed from the apparatus, the apparatus may be displaced or tilted to cause the toner on the cleaning blade and/or the guide plate to drop from a side edge thereof and contaminate the floor or the like.
In view of these, the present invention has been made.